


Fireworks in the East

by Damalia (Achrya)



Series: SnK Modern A/B/O [2]
Category: Shingeki no Kyojin | Attack on Titan
Genre: Alpha/Beta/Omega Dynamics, Alternate Universe - Modern Setting, Anal Sex, Bad Ideas, M/M, Mpreg, Riding
Language: English
Status: Completed
Published: 2016-05-26
Updated: 2016-05-26
Packaged: 2018-07-10 08:35:53
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,349
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6975778
Author URL: https://archiveofourown.org/users/Achrya/pseuds/Damalia
Summary: <blockquote class="userstuff">
              <p>When it comes to sex Reiner and Bertholdt had done just about everything together, except knotting. Reiner, however, is ready to change that. Really ready. Maybe even desperately so. Bertholdt knows it's a bad idea, that he should say no, but he's never been any good at telling Reiner no. </p><p>The thing about bad ideas is that there are usually consequences. </p><p>(A Reibert sidestory for Hanging off the Hinges.)</p>
            </blockquote>





	Fireworks in the East

**Author's Note:**

> Hanging off the Hinges is a JeanMarco story where a one night stand leads to accidental pregnancy. Eventually Reiner and Bertholdt will show up and this is the backstory for their...volatile situation. But if you're just in it for the smut feel free to cruise over the last bit.

If Bertholdt had been thinking, really thinking, when Reiner asked him to come over because he wanted to to try something out he probably would have seen something like this coming. He’d figured it was about sex, as the number of things Reiner might possibly want to try out on a lazy August afternoon when his parents were gone was pretty low, and he’d been right but he hadn’t foreseen  _ this _ . 

But he probably should have. 

After all they’d been fooling around, trying things out together, for a little over a year. They were sort of dating now...or...it was complicated. Or not all that complicated, maybe. 

Reiner had gotten the idea to start ‘trying things out’ after their yearly Sex Education day in school had left him with far more questions than answers. He’d figured that, considering they were best friends and know each other so well, it would work out better than waiting until they found people they actually wanted to date. 

It was practice to make sure they didn’t suck when they found real relationships, was how a very willing Reiner had explained it while climbing into his lap that first time, seemingly unbothered by how he’d reduced Bertholdt to a confused blushing mess. After all Reiner was an omega and Bertholdt was an alpha and it just made sense to try the things they were curious about with each other. Bertholdt had been skeptical about the logic, worried about their friendship and how sex might mess things up and how the fact he had a huge crush on Reiner might affect things and some other things that he’d forgotten about when Reiner had kissed him for the first time. 

He’d said yes in the end. He always said yes to Reiner and would have happily followed him just about anywhere without hesitation. He had been doing just that their entire lives, often into trouble or places he had no business being but that never stopped him from doing it again. He’d never willingly let Reiner blunder into things without him at his side and, in the end, that include sex too. 

They’d started out just watching each other touch themselves then slowly worked up to touching, carefully exploring each other with nervous hands and greedy eyes, getting off by rubbing against each other and then using their hands for that too. They’d kissed between dizzy laughing and then, eventually, put their mouths other places. He’d eventually learned what made Reiner gasp, what made his let out shaky moans, what made him get slick the fastest. He’d used his fingers and tongue inside of Reiner and enjoyed every moment of it. On a sticky summer day two months ago, back in the now criminally small fort they’d once played in, they’d had ‘real’ sex (as Reiner had referred to it even though they both agreed that everything before that had seemed pretty real) for the first time.

It hadn’t been exactly what they’d been hoping for (Bertholdt had orgasmed embarrassingly fast and Reiner would later admit it had mostly just hurt) and the location had been sort of weird, Bertholdt couldn’t even remember why they’d been in there to begin with, and cramped and…

It got better with practice like everything else had. 

Somewhere along the way it had been less ‘friends who were fooling around in the interest of experimentation’ and more of a cuddling after sex or beforesex or just because they were alone and they could, kissing even when sex wasn’t on the table, and holding hands or playing footsie while they did homework together and sleeping curled up each other on weekends. Plus all of the other things that had always been part of being best friends; hanging out, doing things together, late night movies and talks and last minute study sessions and…

They never talked about it or anything but they’d fallen into dating. Or maybe they’d been dating before, because it really wasn’t that much different from how things had been before sex had been folded in. It was hard to say really.

Complicated, but not really. They were still best friends, had grown up across the street from each other and done absolutely everything together their entire lives. It was just that now ‘everything’ was really  _ everything. _

Or almost everything. 

What they hadn’t done was try knotting. Reiner had sort of been hinting that he wanted to give it a go but it wasn’t exactly the sort of thing that could be forced. Outside of a mating bond knotting could only be guaranteed to happen when an alpha was in rut or an omega was in heat. Beyond that it wasn’t the sort of thing that happened often and the handful of times it had, usually when they were going at it a week or two out from Reiner’s heat, he’d always managed to pull out before they were tied. Not that it wasn’t tempting. In the moment, when Reiner was asking for it and holding him closer and clenching around him...Bertholdt doubted anything could be as tempting. 

It was too tempting was the problem. It was easy to get lose himself in Reiner and not just in a ‘I want to knot you’ sort of way, but in a ‘I want to mark you, keep you away from everyone else, and make you mine forever’ kind of way. In the alpha who’d found the person they wanted to mate with kind of way. In the animal sort of way that Bertholdt usually only had to deal with when he was in rut and was suddenly flooded with alpha hormones that made him moody, touchy, and aggressive. And horny. Couldn’t forget that part. 

Something about being with Reiner made all of those things bubble up for reasons he couldn’t begin to define. So, long story short, he was trying to avoid the entire topic of knotting. 

He’d gotten the feeling Reiner had wanted him to stay with him during his latest heat but he hadn’t felt comfortable with the idea. Heats were supposed to have a serious effect of alphas by dragging out their more ‘animal’ side and pushing them to their limits even if the omega wasn’t their mate. With how Reiner already got to him he didn’t feel like adding in a heat or rut was a good idea. He didn’t want to risk losing control and doing something he shouldn’t (like trying to bite Reiner and instigate a mating bond.)

So he’d just pretended he hadn’t noticed the hints and hoped it would be left at that. It was, really, his own fault for assuming Reiner would be so easily put off. His best friend was, after all, one of single most stubborn human beings he’d ever encountered. Once he’d settled on a course of action there was really nothing to do but follow him and hope for the best. 

And he was pretty intent on getting Bertholdt’s knot it seemed. 

Which was how he’d found himself on Reiner’s bed with long legs wrapped around his waist and a lap full of distressingly tempting smelling omega. He knew for a fact Reiner’s heat had come and gone, passing a few days ago, but the scent of it, damp mouthwatering sweetness, clung to his skin still. It called to him like a siren’s song, made him dizzy and frantic. He couldn’t seem to stop himself from pressing his mouth to Reiner’s shoulders, neck, chin, lips. 

He wasn’t entirely sure how he’d gone from letting himself into Reiner’s basement bedroom and finding his boyfriend very naked and touching himself to missing some of his own clothing and leaning back against the headboard while Reiner’s slowly rocked against him. He thought maybe he’d sort of blacked out when he’d set eyes on Reiner with two fingers pressed into his leaking hole, moaning obscenely as he fucked himself. 

Maybe he was just weak. 

It didn’t really matter. 

What mattered was that his dick was rubbing along the crack of Reiner’s ass and that he could feel, intimately, hot wet and hot his boyfriend was, and that he wanted to be in him. Which was a problem. Or. Not really a problem, exactly, except that Reiner also wanted him in. 

Without a condom. 

“I just,” Bertholdt moaned into Reiner’s neck. His nose was pressed against the other’s scent gland; he was drowning in Reiner and that almost too sweet addition that clawed at all the alpha parts of him and wanted more. He wanted to taste it on his tongue, to work his mouth over it, to drive his teeth in.

He settled for a light nip and squeezing Reiner’s ass while rolling his hips up. 

“You just?” Reiner prompted, staring down at him with heavy lidded eyes. His lips were kiss swollen and darker pink than they usually were and everything from his collar bone up was flushed with blood. 

Had he been saying something? 

Oh right. 

“Are you in heat? You smell like.” He could think of any words for it, not with Reiner grinding down on his dick and dragging his tongue over his ear like he was. “Really. Really fucking good. Wanna...ngh.” 

Reiner licked him again, slow and wet, then bit down; Bertholdt’s ability to form words took another hit. He dug his fingers into firm muscle and pushed his face harder against Reiner’s neck, gasping for air that smelled like his boyfriend’s slick and scent and

Fuck him. 

Or Reiner. Whatever. He wasn’t some inflexible alpha who was annoying rigid about the sex thing. He took Reiner however he could get him, happily. 

“Just off my suppressant. I’d always smell like this for a week or two after my heat if I didn’t take them. I thought it might help with things.”

That sounded an awful lot like a set up. 

He really resented how reasonable and together Reiner seemed to be while he was a sweaty stuttering mess. ...which wasn’t that uncommon a phenomena, actually. All the natural confidence and self-assurance alphas were supposed to have seemed to have missed Bertholdt completely while Reiner had all of that stuff in excess. 

“So it’s okay.” Reiner continues between sharp nips to Bertholdt’s neck. His hand found its way into short pale yellow hair, cradling the back of Reiner’s head. “Not in heat. Never been with anyone else. Nothing to worry about.”

Reiner pulled back to meet his gaze. “And. I want you to fuck me and knot me and I want to  _ feel _ it. All of it.” 

And Bertholdt wanted to let him, he really did. He wanted it so much. But. 

“Bad idea.” He managed to gasp out. He gripped Reiner’s hip, forced him to stay still, and tried to remember how talking worked. “Such a bad idea. Not like this.” 

Gold eyes regarded him skeptically. “Why not?” 

Why not? That was a fantastic question. But ‘because my nerves are already frayed and I don’t know what I might do’ wasn’t coming out as easily as he would have hoped. 

“Not...prepared?” 

Reiner blinked at him then was leaning into him again, catching his mouth in a hard kiss. Reiner’s tongue licked over the seam of his lips then slid inside; his hand was pulled away from Reiner’s hip and guided behind him and down.

He groaned into Reiner’s mouth when his fingers were pushed against Reiner’s entrance. He was wet and slick, more so than Bertholdt could ever remember him being, and it only took the barest bit of pressure for his fingers to slide into the slippery hole.

It wasn’t like he’d never had fingers in Reiner before (he had. Plenty of times.) but he felt warmer than he usually did and with the way he was clenching down and pressing back it was pretty obvious he was ready for it. 

It was easy to believe he wanted him inside as desperately as he wanted to be in him. 

“Pretty sure I’m prepared.” Reiner was smirking against his mouth. Bertholdt wanted to tell him that wasn’t what he’d meant at all but his already weak resolve was crumbling. “Please? Bertl, baby, I want this. Want to feel you in me.” 

Such. A. Terrible. Idea. 

He nodded anyway, a little frantically. “Fine. Just...I mean. No knotting.”

He could manage that. He’d always managed to pull out before they were tied before, dealing with the knot by hand, he could do it now. 

Reiner frowned briefly then he lifted up so he was on his knees and wrapped a hand around Bertholdt’s cock. Bertholdt’s fingers slipped free of him then trailed down the back of his thighs. Reiner’s other hand come down on his shoulder, fingers curling, and then he was lowering himself onto his cock.

Reiner didn’t waste any time, pushing himself down and taking all of Bertholdt in with one motion. Bertholdt gasped then groaned, biting his lip and willing himself to not get off embarrassingly fast. It was...he could feel more, the way Reiner’s was tight and fluttering around him, how slick and soft he was inside, and it was more than he’d expected. And it wasn’t that it was some massive difference but...it was different enough.

Better. Felt like they were...closer than usual.

The hand on his shoulder was gripping him tightly and Reiner’s pupils were blown wide. He looked surprised, dazed, and, when he blinked and focused on Bertholdt, hungry. He licked his lips. 

“Good?” 

Bertholdt nodded again. “Y-yeah.” 

He got a smile and a quick, biting, kiss and then Reiner was moving, first in slow shallow bounces that left Bertholdt breathless. His hands smoothed up, feeling thick muscle working as Reiner worked himself up and down his cock, then settled on his boyfriend’s back, wrapping around him to pull him closer in search of more skin to skin contact, more of Reiner.  

Who seemed happy to oblige him, switching his rhythm so he was moving faster, sliding up higher, and then dropping back down with a slap of skin against skin. Bertholdt’s hands spasmed on Reiner’s skin and his hips jerked upwards to meet Reiner’s next downward motion and drive himself deeper into wet velvety heat. Reiner’s breathing stuttered as his body pulsated around him. 

It was hot and getting hotter, both of them dripping sweat as they moved together, filthy squelching noises mingling with panted breaths. He could barely breathe, everything felt so hazy and tight and he was burning up inside, and the intoxicating sweetness of Reiner’s scent was thick in his nose and mouth. Thought was nearly impossible; focusing on anything but Reiner, his omega, was pointless. Reiner’s arms were around his necks, hands, pressing between his shoulder blades. His dick was trapped between them, rubbing against their bellies and smearing thin sticky fluid between them. 

He craned his neck to lick at Reiner’s scent gland again then sealed his lips over it to suck what would undoubtedly be a bruise into his skin. Reiner slowed his movements, writhing under his attentions. 

“Ah. Bert, baby, I-” Reiner gasped wetly. He didn’t finish what he was saying and instead pulled his head up to press their mouths together again, kissing him deeply. It was a messy meeting of lips and tongue, licking and nipping at each other until they were gasping into each other’s mouths. 

When their hips met again Reiner ground down on the base of his dick, hips swiveling in tight little circles. Bertholdt choked, toes curling against the sheets, and let his head drop back to bang against the headboard. Gold eyes slipped shut and a noise that was somewhere between a whine and a purr fell from his lips. The noise, soft, breathy, and unlike his boyfriend but rather something very omegan, went straight to his dick. A growl bubbled up in the back of his throat, slipping free before he could stop it. 

Reiner’s eyes snapped open in clear surprise. Then he smiled toothily and started moving again. Bertholdt matched his movements and used his hands on Reiner’s hips to pull him back when he bounced up. He could feel it, the itchy tightness around the bottom of his cock that came before the inflation of his knot, starting and he knew he needed to be careful but he couldn’t stop himself from fucking up into Reiner harder, dragging him back down greedily.  

Reiner swiveled his hips again, tugging on his hair hard. It didn’t hurt, but was a pleasant tingling crawl over his scalp. “Bert, please. Want to feel it. I need it. Want your knot so bad, need you to do it.”  

He stared at his boyfriend, saw stretched pupils and a wild look on his face. It looked desperate and animal and wanting and Bertholdt wanted it. Wanted to knot Reiner and fill him up and see the look on his face. He could scarcely remember what he’d been worried about. Why would he deny his omega this?

" _Please_." Reiner said, tugging at his hair again. "Need it, Bert, please I- fuck! Oh!" 

The itching faded but the tightness got more incessant and Reiner started to feel tighter around him as his knot swelled to tie them together. Reiner swore again, louder, back bowing and eyes wide, and then he was clenching and trembling around him, locking him in tight and stopping them both from moving. The pressure around him felt good,  _ amazing _ , fluttering around him and snug in a way that was nothing at all like his hand and enough to tip him over the edge. He came with Reiner’s name in his mouth and his eyes shut tight, stomach twisting almost painfully, and spilled into his boyfriend in thick spurts.

There was only the roar of blood in his ears and a feeling like he was floating for a moment. When he came back to himself it was to find Reiner gripping his hair hard enough to hurt and his stomach sticky with the other man’s cum; his eyes were narrowed and his teeth were bared in what looked like a grimace. He was shaking. With the all-consuming need to fuck Reiner gone he was able to think clearly and his first clear thought was that his boyfriend looked like he was in pain. 

“Reiner? You okay?” 

Reiner started to nod then shook his head minutely. “Hurts some?”

Bertholdt’s, admittedly terrible, first thought was to try and undo the tie. Which just resulted in Reiner hissing in pain  and shoving his shoulder hard. He stopped, stricken. He didn’t want to hurt Reiner but...he didn’t know what he was supposed to do. Was it supposed to hurt? He could see where it might if he thought about it logically but no one had ever told him that it would hurt. And if it hurt why did people speak about it like it was the best thing ever?

Everything he’d ever heard about knotting made it out to be an amazing, euphoric, intimate experience. And yet all he felt was nervousness and worry.

“I’m fine. It isn’t that bad.” Reiner said; the tension line between his eyebrows disagreed but Bertholdt couldn’t think of a worse time to argue then when stuck together for an undetermined amount of time. “Help me lie down?” 

He did, carefully rolling them to the side while trying to move as little as possible. Every movement tugged or shifted Reiner him some and he could feel him flexing around his cock and knot. Sparks zipped up his spine and by the time he got them in a slightly more comfortable position, with Reiner's legs still around his waist, he was panting again. 

Reiner glared at him flatly. He smiled sheepishly. 

“Sorry.”

Reiner stayed quiet, regarding him with an unreadable expression that made him want to shrink away. Which he couldn’t. Obviously. Then he was sighing and grinding against him in a slow hip rolling motion. Sparks again and a tightness behind his balls; he stuttered out Reiner’s name and got a cocked eyebrow in return. Another roll, this time with what he was sure was Reiner tightening up around him on purpose, and he groaned, dropping his head into his boyfriend's shoulder. His cock throbbed as it released more cum into Reiner.

Who shivered and moaned. Then blinked owlishly. 

“Okay. That’s...better.” 

“Oh. Maybe I should-”

“Yeah.” 

\---

The knotting did, in the end, turn out to be pretty awesome. Less for how it initially went then for Reiner’s dedication to milking him absolutely dry, but still. Pretty awesome. 

A little internet searching explained that the first time could hurt, especially if outside of pre-heat or heat, when an omega was full of hormones and chemicals that made their bodies more ‘pliable’ as well as made them care about pain (and fatigue. And food. And anything that wasn't sex) way less than they normally would.

There was also a handy footnote about omegas generally liking it when their partners came inside of them which lead to a carefully negotiated agreement to ditch the condoms if Reiner got on birth control instead. Which Reiner had complained about and yes, Bertholdt could understand why taking a pill everyday for the sake of a one week fertile period every three months where they could just avoid sex felt like it was dumb. But it was just a peace of mind thing. Reiner relented when Bertholdt pointed out that, if they could sneak around their parents, birth control meant they could spend some of his next heat together.

An appointment was made and, in the meantime, they agreed to stick with condoms. Bertholdt, personally, didn’t mind. Sex was fantastic either way and he wasn't about to complain about how he got to have it. 

Two weeks before school was due to start up, and the day of Reiner’s physical and first practice of the year for the football team, Bertholdt was busy doing basically nothing when his phone rang. He rolled to the edge of his bed, eyes still focused on his tv, and felt along the floor for where his cellphone had gotten to at some point. 

He glanced down at it, smiling when he saw it was Reiner, then swiped his thumb over the screen. 

“Hey! I thought you’d be-”

“Are you in your room?” Reiner cut him off. He sounded ‘off’, voice high and strained, almost like he’d been running and was out of breath. 

Bertholdt pushed himself up so he was sitting, frowning slightly. “What’s wrong?” 

The only sound coming from Reiner’s phone for a moment was his harsh breathing. The doorbell rang out, echoing through Reiner’s phone. 

“I’m coming in.” 

The call ended. Bertholdt stared at his phone dumbly for a moment then stood up. There was the sound of muffled voices downstairs, one his step-father (the only other person home) and the other obviously Reiner. He pulled open his door and stuck his head into the hall just in time to see Reiner racing up the stairs and turning the corner towards him.

He looked...pale. And scared. 

Bertholdt stepped back to make room, frowning at the bitter note of ‘distress’ clinging to his boyfriend. Reiner pushed the door then, after a pause, pushed the lock in. 

“What are-”

“You know the physical?” Reiner asked, cutting him off again. He was moving around the room, hands wringing together anxiously. “And it’s a thing for omegas when they make us do all that extra shit, like giving them our last heats dates and suppressant brand and having us pee in a cup to make sure we aren’t-”

He stopped there, inhaling sharply, but continued pacing, eyes darting around everywhere except where Bertholdt was still standing awkwardly by the door. It took a minute for him to speak again and when he did it was all in a rush, words running together so that Bertholdt had to stop and puzzle the slurred words out.

“To make sure we aren’t knocked up. Because letting pregnant students get tackled is bad form, I guess.”

Something like dread settling in Bertholdt’s stomach. Why did he feel like he didn’t like where this was going to go?

“And. I. There.” His eyes were glassy and his voice was getting weaker with every word. “I’m off the team. Or benched, really, but I don’t know if...I just.” 

“Why are you benched?” He wasn’t a stupid guy so he was already forming an idea. He didn’t like his idea. 

Reiner glared at him weakly. “Why do you think? Coach Shadis pulled me aside for a ‘private’ talk to tell me then sent me home but I know everyone must know. Why else would I be sent home before we even got to the meeting! And he’s going to have to inform the principal because I don’t fucking know! And this is-”

“Are you saying you’re _pregnant_?” Reiner stopped pacing and, eyes trained on the floor, nodded. The floor jumped up, or Bertholdt sat down; either was he ended up sitting on the floor, staring up at Reiner, stomach roiling dangerously. 

No. No no no. Reiner couldn’t be pregnant, he couldn’t. Omegas had to be in heat to be fertile and Reiner hadn’t...couldn’t. He bit his lip, thinking about how good Reiner had smelled and how hard it had been to control himself, and a dark tendril of doubt curled in his stomach. 

It made him feel sick. 

“How? You weren’t in heat. You said it was fine!”

“I know what I said!” Reiner snapped then, glancing anxiously at the door, dropped back to a urgent whisper. “I don’t know what happened. This...this shouldn’t have happened. It’s not like I did this shit on purpose.”

Before he could say anything back there was a gentle rapping at his door. “Boys? Is everything okay?” 

Reiner’s eyes went as wide as saucers and then he shook his head while mouthing no. Bertholdt didn’t know if that was supposed to mean ‘don’t tell’ or ‘no, everything isn’t fine’. 

The latter, at least, he agreed with. 

**Author's Note:**

> I may, occasionally, have the whim to write things in this universe that are Reibert and don't fit the main story and this is where those things will end up. So. If you're into Reibert and Mpreg and angst and having your heart occasionally stomped on be on the lookout for that.


End file.
